It is known that in measuring the length of a signal or the time between the occurrence of two events, a clock signal of a certain frequency can be applied to the input of a meter circuit belonging to the comparator. By means of a gate, this clock pulse is switched through to the meter only during the signal time that is of interest but otherwise it is blanked out. Thus the meter does not continue to count during the blanked-out segment. If the meter is reset, preferably to zero, during the signal time that is not of interest, the meter reading corresponds approximately to the length of the signal. If the meter is not reset, the difference in meter readings corresponds to this signal length. To compare signal time ratios between two successive periodic events, at least two of these meter circuits are needed and interim storage of intermediate results is necessary when using only one meter circuit in registers. One disadvantage of this, in addition to the extra expense for components, is that a signal time ratio can be obtained only by subtracting the meter readings provided by the meter circuit, and these readings may be estimated as constants.